Simple at its finest
Visuals/Animation: 2.5/3
Audio/Sounds: 2/2
Game play: 4.5/5
Total: 9/10
The Good List: I loved the concept. Lots of exploring, upgrades, a point-combo system, and the general feel of it was relaxing yet fast when the fish started fighting back. The pacing was executed very well too. At first you are fishing for minnows and then you have some "holy crap" moments as you go deeper and realize how small you really are compared to some of the gigantic fish. The fishing fighting each other was a detail that I thought was very cool too. The graphics were great, the controls were smooth and responsive, and the audio/music was very pleasant to listen to.
Suggestions: Usually I do a bad list but honestly, I can't find anything that I can bash you for in this game. Instead I can only provide suggestions to improve it further:
1. Graphics: While the size of the fish in the deepest levels left me in awe for a bit, it wore off as I realized that they are only intricate lines. Imagine the impact if you actually drew out the fish and then drew gigantic sea monsters in the deepest parts of the ocean. Though this all depends on your artistic ability so it could be a hit or miss since I can't gauge your art on this game alone.
2. Varied Upgrades: The upgrade system felt a bit limited. Since you were going for a free roam feel in this game, why not make the upgrades branch out into something more free? For example, customizing attributes like speed/range/health/damage, more tools and weapons, cooler suits, upgrades for the boat, etc. That would bump up the replay value A LOT and people will come back to the game to try out different builds and such.
3. Varied Enemies: In conjunction with drawing out the fish, you could probably come up varied fish that attack differently, swim faster or slower, have tougher scales, and anything else you can come up with. What would also be cool would be to include rare "boss" fish that are hard to take out but give you tons of money for beating them.
I had a lot of fun with this game but it fell short after I beat it because there wasn't too much to do afterwards except fish with overpowered weapons. I feel like this game has a ton of potential and I'm look at the scaffolding for a very good game. I'd love to see how much further you could go with this.
Cheers! ^_^